1. Field of the Invention
The present invention is broadly concerned with an improved dry fractionation process for treatment of xanthophyll-containing vegetative crops which have a high protein content and high fiber constituents to yield a relatively high protein, essentially non-fibrous friable when dry particulate fraction primarily derived from non-vascular plant leaf or petal tissue (hereinafter "high protein xanthophyll-containing essentially non-fibrous fraction"), and a separate tougher, particulate fibrous fraction derived principally from the leaf or petal vascular xylem and phloem network and from the plant stems as well (hereinafter "high fiber fibrous fraction"). These plant fractions can then be individually processed to give high value products. The invention also comprehends a novel fractionating hammermill especially designed for receiving a vegetative crop and efficiently fractionating the crop into a friable when dry high protein fraction and a tougher high fiber fraction. Using the principles of the invention, a vegetative crop treatment facility can be produced at a relatively low cost as compared with prior wet-processing techniques, while nevertheless giving end products having higher value.
2. Description of the Prior Art
Vegetative crops such as alfalfa are known to contain valuable feed components which if efficiently recovered could represent a decided economic advantage. For example, the relatively friable when dry leaf tissue derived portion of 20% protein grade alfalfa contains about 149 mg/lb. of xanthophylls which are valuable as poultry feed supplements. At present day prices xanthophylls have a market value of about $0.50 per gram. Additionally, the protein content of friable when dry alfalfa leaf tissue is significant, ranging from about 20-32% by weight, and usually from about 20-27% by weight. This product presently sells for about $0.22 per pound. Smaller, though none the less valuable quantities of betacarotene, chlorophyll and saponins are also present. Finally, the tougher fibrous stem and leaf vascular system fraction of alfalfa can be used as a ruminant feed, particularly when treated with urea or other non-protein nitrogen source.
As a practical matter, it has proved difficult to efficiently process alfalfa so as to take full advantage of the inherent value of the various components. This is particularly the case inasmuch as alfalfa is not a government subsidized product as are many of the competitive feeds. However, the principal difficulty has been the lack of an efficient technique for extracting the various feed components of alfalfa.
One prior attempt to economically process alfalfa is the so-called Pro-Xan process. In this proposal, fresh-cut, undried alfalfa is macerated in a screw press in order to separate the liquid content of the leaf fraction containing the xanthophylls and soluble proteins. The resultant press cake can then be used as a ruminant feed. The Pro-Xan process has a number of significant drawbacks, however, most notably the capital cost of the necessary plant which in one case was about $25,000,000. Furthermore, wet processing fails to achieve optimum separation of the potentially valuable feed components of alfalfa and is therefore not truly efficient.
Another vegetative crop containing significant quantities of xanthophylls is the marigold plant. The petals of these flowers are processed commercially for their xanthophyll content and have particular utility as a supplement for poultry feeds to enhance the yellow color of poultry skin and of egg yolks. However, in the past, cultivation and harvesting of marigolds for retrieval of xanthophyll rich petals has involved the labor intensive step of picking the flowers by hand. This is required to separate the flowers from the stem and leaf portion of each of the plants.